Stabilizing vinylidene chloride



Patented Nov. 8, 1938 UNITED STATES PATENT OFFICE Dow Chemical Company,

poration oi Michigan No Drawing.

Serial No. 151,721. tion March 23, 1938,

Claim.

This invention relates to the art of stabilizing vinylidene chloride, HzC=CC1:, and to improved compositions thereby obtained.

when vinylidene chloride is exposed to the 5 action of air, light, elevated temperatures, or to any of several catalytic agents, it polymerizes readily forming resinous products, the properties of which will depend to a great extent upon the conditions of polymerization. This tendency to polymerize is so persistent that'it has become necessary to provide a means by which vinylidene chloride may be maintained in the monomeric form at least temporarily, so that it can be stored for a period of time following its preparation and prior to its use in chemical reactions or in resin formation. It is accordingly among the objects of the present invention to provide a means whereby vinylidene chloride may be inhibited against polymerization. A further object is to provide a relatively stable monomeric vinylidene chloride. Another object is to provide a stabilized vinylidene chloride composition from which the stabilizing agent can be readily removed when desired.

I have discovered that vinylidene chloride can be inhibited against polymerization by adding thereto relatively small quantities of certain inorganic compounds, or a combination thereof, and further that the stabilizing agents can again be readily separated from the vinylidene chloride to render the same capable of polymerization. Among the various inorganic materials which I have found to be eflective are strong mineral acids such as concentrated sulphuric acid, concentrated nitric acid, and chlorosulphonic acid.

The concentration of stabilizing agents to be employed in monomeric vinylidene chloride may be varied depending upon the length of time which it is desired to stabilize the compound,

upon the eflectiveness of the particular agent employed, and upon whether any polymerization catalysts have previously been added to the vinylidene chloride. For most purposes a freshly distilled vinylidene chloride will be found to remain in monomeric form if there is added thereto from about 0.2 to about 2.0 per cent of one ofthe aforementioned stabilizing agents. In no case has it been found necessary to employ greater amounts of inhibitor than about 10 per cent of the weight of vinylidene chloride.

In a preferred method of carrying out my invention, a small amount of one of the stabilizing or inhibiting agents previously mentioned, suitably about 0.5 per cent based on the weight ii of vinylidene chloride, is added to freshly dis- Midland, Mich, a corapplication July 2, 1937,

Divided and this applica- Scrial No. 197,616

tilled monomeric vinylidene chloride, which may a Example 1 To two ill-gram mixtures containing 30 per cent vinyl chloride and '10 per cent vinylidene chloride, by weight, were added 0.15 gram each of benzoyl peroxide, chloracetyl chloride, and tetraethyl lead (a known catalyst mixture for the polymerization of vinylidene chloride). To one of the samples was added 1 milliliter of concentrated nitric acid. The two samples were placed in a constant temperature bath at 40 C. for approximately 4 days, at the end of which time the blank had polymerized to a solid while the sample to which nitric acid had been added showed no evidence of polymerization. This sample was subjected to a temperature of 40 C. for an additional period and at the end of a week was still free from evidence of polymerization.

Chlorosulphonic acid and sulphuric acid may be similarly employed to prevent the polymerization of monomeric vinylidene chloride.

This application is a division of my co-pending application Serial No. 151,721, filed July 2, 1937.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the materials employed, provided the steps or materials stated in the following claims he thereby carried out or obtained.

I thereforeparticularly point out and distinctly claim as my invention:

1. A composition of matter comprising monomeric vinylidene chloride and suiilcient of a material selected from the group consisting of nitric acid, sulphuric acid, and chlorosulphonic acid to prevent the polymerization of said vinylidene chloride.

2. A composition of matter comprising monomeric vinylidene chloride and betweenabout 0.2

and about 10 per cent by weight of a material selected from the group consisting of nitric acid, sulphuric acid, and chlorosuiphonic acid to prevent the polymerization of said vinyiidene chicride.

3. A composition of matter comprising vinyiidene chloride and between about 0.2 and about 10 per cent of nitric acid.

momma RALPH M. WILEY. 

